Israel was born as a Jewish state and remains a Jewish state. The US was born as a multi-religious state but with a heavy Christian influence (Sunday blue-laws, Christmas as a national holiday, etc). This oath doesn't say you must be a Jew - only that you acknowledge Israel as a Jewish state. Try being Jewish in arab lands and see true discrimination and pogroms.
Militants loyal to Islamic State claim suicide bombings in Nigerian capital (Reuters)
from the article: Israeli academic: Loyalty oath resembles racist laws of 1935